Seagrass under stress - A measurement and testing design for the assessment of environmental factors in the intertidal zone of the Lower Saxony Wadden Sea

Abstract

Seagrass meadows are a complex habitat and currently under threat, mainly by anthropogenic impacts, like coastal development and eutrophication, but also by extreme weather events, like heat waves and rising marine temperatures due to climate change. The populations of Zostera noltii along the Lower Saxony North Sea coast have significantly declined in recent years, necessitating urgent and intensive investigations to identify the causes in order to take necessary actions. Many studies on seagrass meadows are conducted through direct field investigations. However, these studies have drawbacks, as they can only provide a fragmented picture of living conditions, environmental influences, and changes within a complex ecosystem over time. This is especially true in the intertidal Wadden Sea, where access is limited to a few hours per day. Here, automated measuring instruments that collect data consistently over a long period offer a promising alternative, with the potential to significantly enhance data collection and our understanding of seagrass ecosystems. Here, we present the possible application and advantages of a measurement system for investigating key ecological parameters in intertidal seagrass meadows, including a new expandable measurement station equipped with a multi-parameter probe, current meters, and light sensors. In combination, these devices measure the environmental conditions at low and high tide to show a comprehensive picture of the growing conditions of Z. noltii. We discuss data processing, challenges in application, potential for expansion, and advantages, while also presenting example data. Unlike existing measurement devices, our developed measurement station has the advantage of expandability, accommodating more sensitive water-measuring devices, as well as a large battery capacity. Live data collection via a 3G network is also integrated and can be enhanced by mounting additional antennas. The current meters we use provide long-term, high-resolution current data from the intertidal seagrass meadows, leading to an understanding of the possible mechanical stressors Z. noltii is exposed to. We also applied several filters to the light and temperature data collected by low-cost sensors to extrapolate the attenuation at the seagrass meadows. When used correctly, automated measurement systems have great potential to provide high-resolution data on environmental conditions in Z. noltii meadows, enabling early detection of emerging stressors and facilitating the identification and evaluation of suitable sites for conservation or restoration.